1. Field of the Invention
The present invention relates to a flexible tube to be inserted into a hole and an insertion apparatus including the flexible tube.
2. Description of the Related Art
An endoscope disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2013-97327 discloses a flexible tube for an endoscope which includes a helical tube alternately including a closely-wound region and a sparsely-wound region along a central axis. The flexible tube has adequate resiliency (ease of returning from a bent state), and can be bent smoothly when external force is applied. Therefore, for an endoscope having such a flexible tube, insertability of an insertion section is intended to be improved with respect to a hole.